The epidemiological transmission model for HIV and HCV was applied to IDUs and NSPs specifically in the Northern Territory. The model was used to evaluate current NSPs versus no program and to project likely epidemiological impacts of potential changes to the program. The model estimated the expected number of HIV and HCV cases in the Northern Territory with and without NSP distribution of sterile injecting equipment (Figure 35). The estimated number of infections averted is presented in Figure 36. Less than one HIV infection would be expected due to syringe sharing by IDUs, on average, in the Northern Territory even without NSPs. Thus, NSPs are currently not preventing HIV infections in the Northern Territory. However, NSPs are very effective in averting HCV transmissions. It is estimated that over the last ten years they have averted 483 (458-522, IQR) new HCV infections.

Figure 35: Estimated HIV and HCV incidence in the Northern Territory with and without NSPs

Text equivalent below for Figure 35: Estimated HIV incidence in the Northern Territory with NSPsText equivalent below for Figure 35: Estimated HIV incidence in the Northern Territory without NSPsText equivalent below for Figure 35: Estimated HCV incidence in the Northern Territory with NSPsText equivalent below for Figure 35: Estimated HCV incidence in the Northern Territory without NSPs

Text version of Figure 35

Top of pageFigures in this description are approximate as they have been read from the graph.

Figure 35 consists of four graphs:
  • Estimated HIV incidence in the Northern Territory with NSPs

    • The 100 model simulations decrease gradually from a range of 0.004-0.008 in 1998 to 0-0.005 in 2005 and approach 0 by 2009.

    • The median of the model simulations decreases gradually from 0.005 in 1998 to 0.002 in 2005 and approaches 0 by 2009.

    • The lower quartile of the model simulations decreases gradually from 0.004 in 1998 to 0.001 in 2005 and approaches 0 by 2009.

    • The upper quartile of the model simulations decreases gradually 0.006 in 1998 to 0.003 in 2005 and approaches 0 by 2009.

    • The notification data for annual incidence of HIV in the Northern Territory is consistently below 0.005 for all years between 1999 and 2007.

  • Estimated HIV incidence in the Northern Territory without NSPs

    • The 100 model simulations rise dramatically from 0.002-0.008 in 1998 to 0.025-0.07 in 2000, rise less dramatically to a peak range of 0.01-0.085 during the period 2002-04, decrease gradually to 0.01-0.085 in 2008 and increase slightly to 0.01-0.089 by 2009.

    • The median of the model simulations rises dramatically from 0.002 in 1998 to 0.006 in 2003, decreases gradually to 0.035 in 2008 and increases slightly to 0.036 by 2009.

    • The lower quartile of the model simulations rises dramatically from 0.015 in 1999 to 0.042 in 2003, decreases gradually to 0.022 in 2008 and increases slightly to 0.023 by 2009.

    • The upper quartile of the model simulations rises dramatically from 0.025 in 1999 to 0.078 in 2003, decreases gradually to 0.048 in 2008 and increases slightly to 0.049 by 2009.

    • The notification data for annual incidence of HIV in the Northern Territory is consistently below 0.005 for all years between 1999 and 2007.

  • Estimated HCV incidence in the Northern Territory with NSPs

    • The 100 model simulations remain constant from 1998 to 1999 with a range of 140-250 before decreasing gradually to 0-20 in 2007, where the range remains constant to 2009.

    • The median of the model simulations remains constant at 180 from 1998 to 1999, decreases gradually to 10 in 2007 and remains constant to 2009.

    • The lower quartile of the model simulations remains constant at 175 from 1998 to 1999, decreases gradually to 5 in 2007 and remains constant to 2009.

    • The upper quartile of the model simulations remains constant at 210 from 1998 to 1999, decreases gradually to 20 in 2007 and remains constant to 2009.

    • The notification data for annual incidence of HCV in the Northern Territory is: Top of page
      • 1999 - 90
      • 2000 - 90
      • 2001 - 75
      • 2002 - 70
      • 2003 - 70
      • 2004 - 70
      • 2005 - 70

  • Estimated HCV incidence in the Northern Territory without NSPs

    • The 100 model simulations increase sharply from a range of 120-260 in 1998 to 380-640 in 1999, decrease sharply to 120-210 in 2001 and decrease gradually to 10-40 in 2007 before increasing slightly between 2008 and 2009 to 20-60.

    • The median of the model simulations increases sharply from 180 in 1998 to 500 in 1999, decreases sharply to 150 in 2001 and decreases gradually to 30 in 2007 before increasing slightly between 2008 and 2009 to 40.

    • The lower quartile of the model simulations increases sharply from 170 in 1998 to 480 in 1999, decreases sharply to 120 in 2001 and decreases gradually to 20 in 2007 before increasing slightly between 2008 and 2009 to 30.

    • The upper quartile of the model simulations increases sharply from 210 in 1998 to 540 in 1999, decreases sharply to 170 in 2001 and decreases gradually to 40 in 2007 before increasing slightly between 2008 and 2009 to 50.

    • The notification data for annual incidence of HCV in the Northern Territory is:
      • 1999 - 90
      • 2000 - 90
      • 2001 - 75
      • 2002 - 70
      • 2003 - 70
      • 2004 - 70
      • 2005 - 70

Figure 36: Estimated cumulative number of HIV and HCV cases averted in the Northern Territory due to NSPs

Text equivalent below for Figure 36: Estimated cumulative number of HIV cases averted in the Northern Territory due to NSPsText equivalent below for Figure 36: Estimated cumulative number of HCV cases averted in the Northern Territory due to NSPs

Text version of Figure 36

Top of pageFigures in this description are approximate as they have been read from the graph.

Figure 36 consists of two graphs:
    • Expected cumulative number of HIV cases averted in the Northern Territory due to NSPs

      • With NSPs (current coverage) the cumulative number of HIV cases in the Northern Territory remains consistently below 0.05 for all years between 1999 and 2009.

      • Without NSPs the cumulative number of HIV cases in the Northern Territory increases gradually from below 0.05 in 1999 to 0.05 in 2009.

    • Expected cumulative number of HCV cases averted in the Northern Territory due to NSPs

      • With NSPs (current coverage) the cumulative number of HCV cases in the Northern Territory increases gradually from 200 in 1999 to 700 in 2009.

      • Without NSPs the cumulative number of HCV cases in the Northern Territory increases sharply from 500 in 1999 to 1,100 in 2001 and continues to increase gradually, reaching 1250 by 2009.